Orders for the final two tunnel boring machines (TBMs) for Crossrail have been placed with Herrenknecht.
The last two TBMs – out a total of eight machines needed for the project – will be used to bore the Thames Tunnel in south east London, which is being undertaken by a joint venture of Hochtief Construction and Murphy & Sons.
The 2.6km long Thames Tunnel will be built using slurry TBMs, rather than earth pressure balance machines that will be used elsewhere on the project, in order to cope with the ground conditions in the chalk through which the tunnels will be bored. The 6m diameter tunnels elsewhere on the scheme will be bored through the London clay, sands and gravel.
Hochtief and Murphy expect to launch the Thames Tunnel TBMs from the Plumstead Portal towards the North Woolwich Portal late next year. Construction at Plumstead is already under way and work at North Woolwich is due to start in early 2012.
Manufacturing of the other six TBMs for Crossrail is also being carried out by Herrenknecht and the first is due to be delivered to the Royal Oak Portal site at Paddington late this year.